Deconstructing "K&R C"

Post by halayli » Wed, Jan 11, 2012, 7:55 AM UTC

zedshaw wrote: post #69

halayli wrote: post #57

The function copy expects a C style string but he pass a buffer to some data. If you pass it the proper argument you'll get a proper result, it's that simple. I see the complaint is more about C style strings in general because it's easy to corrupt them by overwriting NULL at the end rather than a complaint about "K&R C" book. I don't get why he decided to put it under this title.

The problem is in the word "expects". This function expects certain things but doesn't assert that they're happening. Because of this you get bugs when you try to use that function in other code, which is what beginners do. And yes, the solution is to require a size with every string buffer, which is what I do nearly all the time now. But, the best way to learn why that's solution is to try to hack something with thi…

Post by silon3 » Wed, Jan 11, 2012, 8:24 AM UTC

scott_s wrote: post #33

adavies42 wrote: post #20

> Braces Are Free, Use Them I disagree. Braces have a cognitive load, particularly if they're given whole lines to themselves. Which is easier to read, while ((len = getline(line, MAXLINE)) > 0) if (len > max) { max = len; copy(longest, line); } if (max > 0) /* there was a line */ printf("%s", longest); or while ((len = getline(line, MAXLINE)) > 0) { if (len > max) { max = len; copy(longest, line); } } if (max > 0) /…

Because it's the style I use, and because I don't need to bug-check the indented code to make sure it's braced correctly, I find this easiest to read: while ((len = getline(line, MAXLINE)) > 0) { if (len > max) { max = len; copy(longest, line); } } if (max > 0) { /* there was a line */ printf("%s", longest); }

Post by ec429 » Wed, Jan 11, 2012, 9:17 AM UTC

zedshaw wrote: post #83

marshray wrote: post #41

Earlier quoted context omitted.

To be pedantic, it's not that strcpy is making assumptions . Its interface is defined such that it is explicitly invalid to pass it some other garbage.

To be both pedantic and correct, there is no way to define a C function to restrict a string input so that it is correctly terminated. So no, it's at best documented that you shouldn't do that and definitely doesn't prevent you from doing this.

Post by NickPollard » Wed, Jan 11, 2012, 11:41 AM UTC

SeanLuke wrote: post #24

adavies42 wrote: post #20

> Braces Are Free, Use Them I disagree. Braces have a cognitive load, particularly if they're given whole lines to themselves. Which is easier to read, while ((len = getline(line, MAXLINE)) > 0) if (len > max) { max = len; copy(longest, line); } if (max > 0) /* there was a line */ printf("%s", longest); or while ((len = getline(line, MAXLINE)) > 0) { if (len > max) { max = len; copy(longest, line); } } if (max > 0) /…

I'm probably the last person in the world to prefer: while ((len = getline(line, MAXLINE)) > 0) if (len > max) { max = len; copy(longest, line); } if (max > 0) /* there was a line */ printf("%s", longest); I fear this may be literally true: this brace style is called Whitesmith's, and I was reporting bugs to the cc-mode indenter for emacs a while ago. BSD/Allman and K&R styles never made sense to me.

  while ((len = getline(line, MAXLINE)) > 0)
      if (len > max) {
          max = len;
          copy(longest, line);
          }
    
      if (max > 0) /* there was a line */
          printf("%s", longest);

Post by tptacek » Wed, Jan 11, 2012, 2:15 PM UTC

aaronblohowiak wrote: post #91

tptacek wrote: post #88

Earlier quoted context omitted.

High level string libraries are a win. But you may be overstating your case a bit. From my codebase/third-party directory on my laptop (a bit random, I admit), from those projects I'd consider "competent C" (ie, not OpenSSL or MRI ruby): * dovecot uses ASCIIZ strings and libc string functions * redis uses ASCIIZ strings and libc string functions * nginx uses a high-level buffered string library * lcamtuf's skipfish s…

Redis strings are actually length prefixed null terminated strings